Prosthetic rehabilitation of patients with maxillary oncology defects using zygomatic implants

Purpose Prosthetics for patients after oncological resection of the upper jaw is a complex problem associated with the physiological and anatomical separation of the oral cavity and the nasal/paranasal region. This study reports the clinical results of the use of the zygomatic implants for prosthetic rehabilitation in patients with maxillectomy due to upper jaw tumors. Materials and methods The study included 16 patients who underwent prosthetic rehabilitation using a zygomatic implant after maxillectomy period from 2021 to 2023. After the tumor was removed, immediate surgical obturators were placed. Main prosthetic rehabilitation was performed 6–12 months after tumor removal, but before that, a temporary obturator was made and used. Six-twelve months after tumor resection, 1–4 zygomatic implants were inserted into the zygomatic bone unilaterally or bilaterally. A total of 42 zygomatic implants were installed, 2 of which were unsuccessful and were removed in 1 patient. The implants were placed using the surgical guide, which was planned and prepared digitally. Results No postsurgical complications were seen, and the patients were discharged from the hospital after 7–10 days. The patients were able to return to a normal diet (hard food) after just 7 days following surgery, with no further complaints regarding function or pain, apart from the residual edema caused by the intervention. Conclusions The use of prostheses fixed on zygomatic implants in patients with maxillary defects is an effective method of prosthodontic rehabilitation in complex clinical cases after maxillectomy.


Introduction
Malignant tumors of the nasal cavity and paranasal sinuses account for 1.4% of the total number of cancer cases.Involvement in the tumor process of upper jaw most bone structures is a secondary lesion that begins from the epithelial cover of the mucous membrane of the maxillary sinus, ethmoid labyrinth, nasal cavity, alveolar process or hard palate [1].
Treatment of cancer patients is one of the most difficult pathologies of the human body [2].During therapy, various complications may occur, including tooth loss [3][4][5][6].It is proposed to restore the integrity of the dentition, including the use of dental implants [7][8][9].But since the implant procedure is associated with certain difficulties, it is important to analyze whether it is even possible to carry out such an intervention in the treatment of oncological pathologies.Implant treatment requires good health [10].
Contraindications for implant therapy are chemotherapy and radiation therapy because they cause cell death, including those responsible for immunity.These negative effects interfere with the normal healing process after implant therapy and may be an indirect cause of tissue infection around the implant [7,11].
During the period of remission, when health indicators have stabilized, an attempt at implant therapy can be made, but it is important to understand that the risks in this case are slightly higher than in patients without a history of cancer [12][13][14][15].
The possibility of prosthetic treatment in the presence of a tumor disease is influenced by its location, nature, treatment received and type of structure [16][17][18][19][20].If the cancer is located outside the maxillofacial area, this is a very conditional contraindication to orthopedic treatment [21,22].
The decisive factors here are the nature of the neoblastoma formation and the treatment taken in connection with it.The main concerns in this case may be related to a violation of the blood clotting process.Very often, to prepare a patient for removable or fixed prosthetics, it is necessary to resort to preliminary surgical preparation, which is necessarily accompanied by local bleeding.If a tumor disease affects the hematopoietic system, or the patient receives radiation during treatment, blood clotting is significantly impaired [23].As a result, this can lead to local bleeding that poses a great threat to the patient's life, therefore, in such cases, manipulations associated with rupture of blood vessels should be avoided whenever possible.
The fact is that very often such patients are treated with drugs from the bisphosphonate group.Long-term use of bisphosphonates leads to the fact that extensive bone necrosis may occur during tooth extraction or preparation of the alveolar ridge for a prosthesis [24,25].
If dental prosthetics for oncology is carried out against the background of immunosuppression or therapy that suppresses the immune system, you should work very carefully when preparing and forming the basis of the prosthesis [26].The formation of microtraumas and rubbing in this case can lead to long-term non-healing lesions.In this case, planning orthopedic treatment is very difficult.Dental prosthetics for oncology with this arrangement should be postponed [27][28][29][30][31][32][33][34].
After therapy or radical removal of the tumor, implants in the remaining parts of the jaw or installation of zygomatic implants may be performed [35][36][37].Installation of zygomatic implants is one of the treatment options for patients with insufficient bone tissue in the upper jaw or after radical surgery to remove a tumor (38)(39).
The standard modern treatment for upper jaw carcinoma is radical surgical removal of the tumor followed by radiation or chemoradiotherapy.The location, morphological structure and size of the tumor determine the boundaries of resection.The severity of functional defects depends on the size of the defect.and cosmetic disorders.
Treatment of midface tumors is a complex area of head and neck reconstructive surgery.After radical resections, forming extensive defects of the upper jaw, communicating with the maxillary sinus, nasal cavity, oral cavity and orbit.With such defects, the patient experiences severe functional disorders: the act of chewing, swallowing and, as a result, it becomes impossible to take solid and liquid food, changes speech (pronunciation of sounds), chronic mucositis [40,41].
Not only the surgical procedure is complicated, but also the choice of optimal methods of prosthetic rehabilitation, since the use of standard obturators often leads to the development of contact mucositis, and disruption of the occlusal relationships of the jaws leads to dysfunction of the temporomandibular joint.As a result, the patient's quality of life noticeably deteriorates, which causes social maladjustment and psychological disorders.
In case of extensive postoperative defects of the upper jaw, the lack of retention points for a removable plate prosthesis (obturator) prevents its use [42,43].Due to insufficient bone tissue, the installation of conventional dental implants after resection of a malignant tumor of the upper jaw to fix prostheses is often difficult.
Zygomatic implants provide a predictable solution for restoring dentition and facial structures affected by malignant diseases of the upper and midface.Combined use of dental and zygomatic implants may help restore oral function in patients with severe maxillary defects [38,44].In such cases, an alternative may be zygomatic intraosseous implants of the Zygoma type, providing the possibility of rational dentofacial prosthetics [45][46][47].
For the first time, implants that are attached to the zygomatic bone were used by P.I.Branemark et al. in 1993 [51].Zygomatic implants are installed in different ways: bilateral two implants, bilateral with one implant, unilateral with one or two implants and in combination with conventional dental implants [47].In 1997, Weischer et al. suggested using intraoral implants fixed in the zygomatic bone for mechanical support of the obturator prosthesis after hemimaxillectomy [49].Later, other authors also presented long-term results of using implants Zygoma type with immediate loading capability.Implantation was successful in 96.8% of cases [50][51][52].Since 2008, the method of zygomatic intraosseous implantation has been recommended for use with immediate load [45,53].It provides good stabilization prosthetic obturator due to bone support.This prevents the prosthesis from moving, food and liquid entering the nasal cavity, and eliminates the occurrence of chronic inflammation and contact mucositis.
Effective use of dentures supported by zygomatic implants and dental implants can provide complete functional and aesthetic rehabilitation in patients with postresection severe defects of the upper jaw [54].

Materials and methods
The study included 12 patients who underwent prosthetic rehabilitation using zygomatic implants after maxillectomy for maxillary tumors between 2021 and 2023.There were 9 male patients and 7 female patients with an average age of 54.8 years old.Research was undertaken with the approval of the Institutional Review Board.
In order to clarify the diagnosis, and then plan and select a surgical method, a set of diagnostic methods was carried out.The type of tumors was determined by CT, MRI methods, and histopathological examination.
The distribution of lesions was the following: 5 benign and 11 malignant.Seven patients have undergone radiation therapy before or after implant placement.After the tumor was removed, immediate surgical obturators were placed.Main prosthetic rehabilitation was performed 6-12 months after tumor removal, and before that, a temporary obturator was made and used.Six to twelve months after tumor resection, 1-4 zygomatic implants were inserted into the zygomatic bone unilaterally or bilaterally.

Results
A total of 36 zygomatic implants were installed, 2 of which were unsuccessful and were removed in 1 patient.No post-operative complications were reported, and the patients were discharged from the hospital after 10 days.The patients were able to return to a normal diet (hard foods) after just 7 days from surgery, with no further complaints regarding function or pain, apart from the residual swelling caused by the intervention.Prosthetic rehabilitation began after tumor removal and an immediate temporary obturator was made.
Patients' health-related quality of life (HR-QOL) before treatment was ≥ 48.3%.HR-QOL and overall quality of life after rehabilitation was rated as ''good'' by 76.8%, respectively.In all cases chewing was also the most important function for the patients, (preimplantation 26.4% and post 67.3%) masticatory function scores increased after prosthodontics treatment with implants.In this clinical case we show the use of intraosseous zygomatic implants for prosthetic rehabilitation in patients with maxillectomy for tumors of the maxilla.

Clinical report
On May 14, 2023, patient A.A., 64 years old, was admitted to the clinic with a diagnosis of a condition after maxillofacial resection of the left side.The anamnesis showed that on March 30, 2021, a left maxillectomy was performed for cancer of the mucous membrane of the left maxillary sinus (T4N0M0).The patient received preoperative and postoperative radiotherapy.
At the time of admission, the general condition was stable, an oral cavity defect was detected in the area of the left half of the upper jaw, the mucous membrane was normal, without visible changes.The patient wore a removable denture.A general laboratory study results showed that the laboratory parameters were normal, according to CT data, the condition after resection of the upper jaw on the left side was complete edentulism, bone resorption.It was planned to install 2 zygomatic implants on the left side, 1 on the right side and immediate rehabilitation with complete removable dentures, which would be immediately connected to the multi-unit zygomatic implant abutments.After 6 months, the final dentures were installed.The treatment plan was pre-agreed with the patient.The installation of the zygomatic implant was carried out under general anesthesia according to plan; after the operation temporary prostheses were installed and screwed to the implants.After 6 months, final rehabilitation was carried out with removable dentures connected to a multi-unit abutment of the zygomatic implant.A removable window was formed in the palatal part of removable dentures for hygiene: this movable part of the plate was fixed to the main fixed part of the denture using magnets.After rehabilitation, the patient was satisfied with the results of treatment, chewing function was restored, and the quality of life improved (Figs. 1, 2, 3, 4, 5, 6, 7 and 8).

Discussion
Malignant neoplasms account for almost half of the pathologies that are indications for resection of the maxilla [27,55].Maxillectomy for malignancy often results in a maxillary defect and severe oral dysfunction [56,57].The choice of method for surgical rehabilitation of patients after tumor resection depends on a number of key points, such as the patient's age, the presence of concomitant pathology, size of the defect, as well as the professional skills of the surgeon [58].Microsurgical reconstruction increases the duration of hospital treatment, morbidity in the donor area, and the incidence of complications in both the recipient and donor areas, and also limits the possibility of direct visual diagnosis of disease relapse [59,60].
The use of removable dentures supported by implants, on the contrary, allows for full rehabilitation of a patient in a short time, since it does not cause additional trauma associated with the donor site.A removable or partially removable denture allows you to inspect the surgical site In patients who have undergone a complete or partial maxillectomy, the use of zygomatic implants is one of the main methods to help support obturators and/or removable dentures [63,64].
The use of computer-aided design and computer-aided manufacturing (CAD-CAM) technologies can help in the prosthodontics rehabilitation of patients with post-resection oncological defects of the maxilla [65].
Maxillectomy for malignancy often results in a maxillary defect and severe oral dysfunction.The effective use of dental and zygomatic implants can help restore oral function in patients with severe maxillary defects.In the example we described: during 1 operation it was possible to perform resection of the upper jaw and install 3 intraosseous implants, which became a support for prosthetic obturator.This has significantly reduced rehabilitation period and quickly returned the patient's ability to chew, swallow, speak normally, and brought a good aesthetic results.The total duration of treatment and rehabilitation was 1 month.Research results indicate that the use of zygomatic implants provide full functional and aesthetic rehabilitation of cancer patients, even in cases of extensive defects of the upper jaw.The effective use of dental and zygomatic implants can help restore oral function in patients with severe maxillary defects.

Fig. 2 Fig. 1
Fig. 2 Clinical image showing after installation of implants and multi-unit abutments

Fig. 4 Fig. 3 Fig. 8
Fig. 4 Radiological images.Postoperative CT after installation of 2 zygomatic implants on the right side and 1 on the left side